a. Field of Invention
The invention relates generally to automotive instrument panels having automotive Passenger Side Inflatable Restraint (PSIR) components, and more particularly, the invention relates to a system and method for scoring an automotive milled PSIR door system to increase the bending strength of a common tear line to improve performance and long term aesthetics.
b. Description of Related Art
Automobiles are commonly equipped with airbags for reducing driver and passenger injuries in the case of an accident. Automobile airbags are generally located in areas where a driver or passenger would potentially contact an automobile interior in the event of an accident. Airbags can reduce injuries by providing a substantially non-solid surface for the driver or passenger to contact, as opposed to the generally solid surfaces of the automotive interior. Although the functionality of the airbag is greatly valued, the visual appeal of the instrument panel and invisibility of the airbag system are also of value to automobile manufacturers and consumers alike, as it leaves the general surface styling uninterrupted. Known airbag systems with seamless designs exist where there is virtually no indication on the outer surface of the instrument panel that the airbag is behind the instrument panel. Thus, any seams or tear lines provided in the instrument panel are only provided on the underside and not on the exposed side of the instrument panel.
In order to install an airbag, the airbag is generally folded into a module that is installed into and behind an automotive instrument panel component. The module housing a Passenger Side Inflatable Restraint (PSIR) is generally installed on the underside of an instrument panel, with a PSIR chute between the instrument panel and PSIR module. The instrument panel generally has pre-weakened lines, invisible when viewed from the top, forming one or two doors allowing the airbag to release therethrough. A PSIR chute is typically bonded to the instrument panel and generally includes PSIR doors that line up with the pre-weakened lines on the instrument panel. For example, FIG. 1 is an environmental perspective view of an automobile interior 10 having an exemplary instrument panel 12 and windshield 13, where instrument panel 12 contains on its underside a section view of a conventionally mounted PSIR system 14.
As is known in the art, instrument panel PSIR doors may generally include a U-shaped or H-shaped weakening pattern for facilitating adequate opening of the PSIR doors during air bag deployment, as well as for allowing deployment of the passenger air bag at an optimal trajectory. For example, FIG. 2 is a diagram illustrating exemplary deployment characteristics of a typical PSIR air bag. Referring to FIG. 2, a passenger P is positioned on the passenger side of an automobile interior in front of instrument panel 12 and windshield 13, and deployed airbag 15 must open at a substantially oblique trajectory T relative to forward PSIR door 20 and rearward PSIR door 18. FIG. 3 is a fore-aft sectional view of a conventional PSIR system having an H-shaped pattern PSIR door system. Referring to FIG. 3, a conventional H-shaped pattern automotive PSIR door system 14 is shown in cross section and generally includes rearward PSIR door 18 that can open toward passenger P (see FIG. 2) and forward PSIR door 20 that can open toward windshield 13 (see FIG. 2). PSIR doors 18, 20 may be formed from an instrument panel outer layer 16, and may be hingedly connected at hinges 22, 24, respectively, to chute 29. Chute 29 may include chute sidewalls 32a, 32b, and chute end wall 33 connected by connectors 31 to an airbag canister 62. PSIR doors 18, 20 are further coupled at common tear line 26, and may have side tear lines 28, 30 completing the H-shaped door pattern which opens during airbag deployment. The common tear line and side tear lines are weak areas of reduced thickness that are designed to tear and/or break when an airbag inflates and forces the PSIR doors open. An airbag 34 is contained within and coupled to chute 29 and is deployed through PSIR doors 18, 20 upon deployment. Common tear line 26 is typically a straight line or a linear design in conventional PSIR system door designs. For example, FIG. 7 is top plan view of a conventional PSIR door design and deployment region where the common tear line is a straight line. As shown in FIG. 7, a top plan view of a conventional PSIR system door design is shown, including rearward PSIR door 18 and forward PSIR door 20, hinges 22, 24, common tear line 26, and side tear lines 28, 30. In such conventional PSIR door designs, the common tear line 26, which is the only segment in the scoring pattern which is not supported by chute 29 (FIG. 3), can be easily bent. Such a common tear line can be formed by milling, cutting, grinding, or other known techniques. Typically, such a common tear line that is formed by milling and hidden from view can become bent or weakened due to various factors, including but not limited to, manufacturing stresses such as from the milling process itself, thermal effects, material shrinkage, physical attachments of the airbag to the PSIR door system, environmental loads such as temperature variations including extreme heat or cold, and passenger or occupant mistreatment such as a passenger or occupant putting his or her feet on or against the instrument panel, thereby putting pressure on and weakening the invisible common tear line. For example, FIG. 4 is an enlarged view of the common tear line portion of FIG. 3 illustrating distortion in the area of the common tear line. As shown in FIG. 4, a close-up of common tear line 26 is shown between PSIR doors 18, 20. The assembly method for chutes to hard instrument panels is typically vibration welding which produces melting of the plastic in both components where they contact, and which upon cooling, induces thermal shrinkage and stress in contact area 35 to cause compression in contact area 35 and tension in the opposite visible area 36 of the instrument panel outer layer 16. Further, the thermal shrinkage in contact area 35 can also cause bending in area 37 at common tear line 26.
Fragmentation or the launching of broken shards of plastic toward the occupant is to be avoided during deployment. The presence of bridge pieces 42 (see FIG. 5) produced during milling of the tear or score line, which act to increase the bending strength of score seams for aesthetic purposes, increases the tendency for such fragmentation. Thus, it is desirable to minimize or eliminate the number of bridge pieces that can potentially break off or fragment while still providing strength to the instrument panel and PSIR door system.
It would therefore be beneficial to provide an economical and efficient system and method for scoring an automotive milled PSIR door system that addresses the issues with existing systems and methods, and that minimizes and/or eliminates one or more of the above-identified deficiencies.